Forging machine for the internal profiling of tubular workpieces, particularly of barrels for firearms



p 13, 1965 B. KRALOWETZ 3, 7

FORGING MACHINE FOR THE INTERNAL PROFILING OF TUBULAR WORKPIECES, PARTICULARY OF BARRELS FOR FIREARMS Filed Dec. 22, 1961 4 Sheets-Sheet 1 film/0 M44 0 5 E 14.0

April 13, 1965 a. KRALOWETZ FORGING MACHINE FOR THE INTERNAL PROFILING OF TUBULAR WORKPIECES, PARTICULARY OF BARRELS FOR FIREARMS 4 Sheets-Sheet 2 Filed Dec. 22. 1961 a w n M M a M 0 K HHF R vfLTl% 5% .3 mm n .nHnHHMMnHHHHHHHHH B. KRALOWETZ April 13, 1965 FORGING MACHINE FOR THE INTERNAL PROFILING OF TUBULAR WORKPIECES, PARTICULARY OF BARRELS FOR FIREARMS 22, 1961 4 Sheets-Sheet 75 Filed Dec Qua 1 3 April 13, 1965 B. KRALOWETZ 3,177,688

FORGING MACHINE FOR THE INTERNAL PROFILING OF TUBULAR WORKPIECES, PARTICULARY OF BARRELS FOR FIREARMS Filed Dec. 22. 1961 4 Sheets-Sheet 4 United States Patent 3,177 ,688 FORGING MAtC FOR THE INTERNAL PRO- FILING 0F TUBULAR WORKPIECES, PARTICU- LARLY 0F BARRELS FOR FIREARMS Bruno Kralowetz, St. Ulrich, near Steyr, Austria Filed Dec. 22, 1961, Ser. No. 161,531 Claims priority, application Austria, June 6, 1961, A 4,381/61 4 Claims. (Cl. 72-21) This invention relates to forging machines for shaping the internal profile of tubular workpieces, particularly of barrels for firearms. It is known to use for this purpose a stepped mandrel for shaping the cartridge chamber at the same time as the barrel. Moreover, it is known to grip the workpiece between longitudinally spaced stops while it is being forged in order to obtain a more exact internal profile. Such gripping reduces length changes of the workpiece during forging and increases the penetration of each hammer blow. In a known forging machine for carrying out this process, the workpiece is gripped between a gripping head, which feeds the workpiece toward the hammers and at the same time rotates it about its axis, and a holder-up. The latter is moved backwardly by the feed movement of the workpiece against the pressure of a liquid. The back-pressure exerted by the holder-up on the workpiece in opposition to the feeding force determines the force with which the workpiece is gripped in its longitudinal direction during forging. It remains constant in the known machine. It has been found, however, that a constant gripping force does not give satisfactory results with tapered workpieces such as the tapered barrels used in automatic firearms. As the wall thickness of the workpiece increases, the penetration of the hammer blows decreases, and it would be necessary also to taper the outside of the barrel in order to obtain a well-defined internal profile throughout the length. of the workpiece since the constant longitudinal gripping force cannot correspond to the largest wall thickness of the workpiece. The same difiicnlties arise when the cartridge chamber is to be formed in the same forging operation immediately after the barrel. The gripping force required for forging the barrel is much smaller than that which is needed while the cartridge chamber is being shaped. After a sharp-edged step or shoulder has been formed by hammering the workpiece on the corresponding portion of the mandrel, the workpiece is stretched as it is fed further while being hammered, and the flow of material in the axial direction forces the internal edge, previously formed by hammering, away from the corresponding step or shoulder of the mandrel so that the mandrel step is once more impressed into the material at the next hammer blow and multiple steps, which are not well defined, are obtained.

It is an object of the invention to provide a forging machine which eliminates these disadvantages and which enables a satisfactory internal profiling of workpieces which are tapered or are to be provided with internal steps.

The invention in its more specific aspects is concerned with an improvement of the known forging machine in which the holder-up moves backwardly in accordance with the feed movement of the workpiece against a con stantly applied back-pressure of a liquid, Which is being displaced. The improvement resides essentially in means for automatically varying the back-pressure of the liquid in accordance with the wall thickness and/or the desired internal shape of the portion of the workpiece disposed between the hammers. Such means may consist of a valve incorporated in the return conduit for the pressure liquid. The force with which the workpiece is gripped in its longitudinal direction is increased with an increase 3,177,688 Patented Apr. 13, 1965 in the wall thickness or when an internal step or the like is being forged so that a satisfactory forging is obtained.

The valve provided in the return conduit may be controlled remotely by a feeler which scans a template dur-i' ing the feeding movement of the gripping head.

The shape of the template corresponds to the changing wall thickness of the workpiece or to the desired internal shape of a certain portion of the workpiece. The backpressure of the holder-up and the gripping force are automatically varied in accordance with the scanned shape of the template during the feed movement of the workpiece.

While an internal step is forged at the transition from the barrel to the cartridge chamber, the back-pressure or the force with which the workpiece is gripped in its longitudinal direction must be considerably increased, as has been mentioned hereinbefore, in order to prevent the pre-' viously hammered internal edge from being forced away from the step of the mandrel by axial flow of the material. It has been found that this measure alone may .not be suflicient in some cases to ensure the shaping of a well-defined step. For such cases, that portion of the gripping head which supports the workpiece at one end has a protruding annular portion of smaller outside diameter than the workpiece, or the latter has an annular recess adjacent the gripping head. During forging, the material slides over this protruding annular portion, or the annular recess is upset so that the gripping in the longitudinal direction in conjunction with the forging force applied by appropriately shaped hammers results in an axial flow of material in the direction toward the gripping head only, and the forged internal edge cannot be forced away from the step of the mandrel.

When the barrel and cartridge chamber are forged in one operation, that portion of the mandrel which conforms to the grooves and lands of the barrel is first placed between the hammers, and the workpiece is gradually pushed over the mandrel. During the final phase of the forging operation, the mandrel together with the workpiece follows the feed movement of the gripping head to cause an enlarged portion of the mandrel to enter the space between the hammers so that the cartridge chamber can be forged. To enable this operation to be performed automatically, the mandrel is connected to a pis ton slidable in a cylinder by a rod freely extending through the gripping head. Liquid under pressure can be applied to the cylinder which is independently displace-1 able against a hydraulic resistance so that the mandrel, which is otherwise movable independently of the gripping head, engages a surface of the gripping head and is moved by the latter during the final phase of the feed movement of the workpiece.

An embodiment of the invention is shown by way of example in the accompanying drawings, in which FIGS. 1A and 1B are partlysectional respective views of the forging box with the holder-up and of the gripping head with the gripping head bed of a forging machine;

FIG. 2 shows the hydraulic circuit for varying 1 the back-pressure of the holder-up;

FIG. 3 is an enlarged sectional view of a pressurecontrolling valve in the circuit of FIG. 2;

FIGS. 4 to 6 are sectional views illustrating the forging of a barrel with cartridge chamber on the machine of FIGS. 1A and 1B; and

FIG. 7 shows the end of a modified workpiece intended to cooperate with a modified gripping head.

The forging hammer-s 1 and their drive means, not shown, as well as the means for varying their stroke position, are mounted in a forging box 1, in front of which the bed 2 for the displaceable gripping head 3 is disposed. The rods 4 of pistons 5 sliding in cylinders 6 extend through the forging box 1' and are secured to the gripping head 3. When hydraulic fluid under pressure is admitted to the cylinders 6 in a conventional manner, the pistons are reciprocated and cause the gripping head 3 to perform a feed movement toward thehammers 1 or a return movement. A sleeve 7 gripping the workpiece is rotatably mounted in the gripping head 3 and is driven by means of a worm gearing 8 by a motor, not shown.

The forging box 1' is provided with a tubular guide 9 for a rotatable holder-up 10 which is backed by a piston 12 slidabie in a cylinder 11. A rod 15, which extends free ly through the gripping head 3 in the sleeve 7, connects a forging mandrel 13 or 14 to a piston 16 sliding in a cylinder 17. The cylinder 17 is axially displaceable between stops in a cylinder 18 fixed on the bed 2. The cylinde'rs 17 and 18 communicate through bores 18' in a radial wall of the cylinder 17 through which the rod passes. The pressure fluid conduit 19 opening into the cylinder 18 is constantly under pressure whereas pressure may be intermittently applied to the cylinder 17 through a conduit 20. Because the effective area of the right radial end face of piston 16, as viewed in FIG. 2, is larger than that of the left end face, the piston 16 and the mandrel 13 or 14 can be reciprocated in spite of the continuous application of pressure through conduit 19 by pressure fluid admitted to or released from the cylinder 17 through conduit 20.

The workpiece, which is a tapered barrel 21 (FIGS. 1A and 1B) or a cylindrical barrel 22 (FIGS. 4 to 6), is gripped between the holder-up 10 and the sleeve 7 of the gripping head 3. During the feed movement of the pistons 5 and the resulting movement of the holder-up 10, the piston 12 drives oil from the cylinder 11 through a conduit 23, a pressure-setting piston valve 24 and a conduit 25 into a container 26, as shown in PEG. 2. A control valve 27 is provided for controlling the pressure-setting valve 24 and is shown in more detail in FIG. 3. The gripping head 3 carries a template 28, which is scanned by a feeler 29 during the movement of the gripping head. Depending on the position of the feeler 29 determined by the template 28, a spring 31 applying pressure to a Valve cone 32'} of the control valve 27 is more or less stressed. The piston 32 of the pressure-setting valve 24 is biased by a spring 31' toward a position in which the piston 32 blocks the orifice of the conduit 25. The piston 32 is formed with a narrow bore 33, through which oil is continuously supplied at a low rate through a conduit 34 to the pressure-controlling valve 27. The oil returns from the valve 27 through a conduit 35 to the oil container 26.

When the feeler is forced by the template 28 into the housing of the control valve 27 during the movement of the gripping head 3, the spring 31 acting on the valve cone 31 is more highly stressed, and the pressure in the conduit 34' is increased. The increased pressure in the conduit 34 and the force of the spring 31' displace the piston 32 of the pressure-setting valve 24 downwardly, as viewed in FIG. 2, against the pressure applied to its underside through a branch conduit 36. The controlling edge 37 of the piston 32 thereby increasingly obstructs the orifree of the conduit 25 so that the pressure in the return conduit 23 increases as well as the pressure on the holderup 10. When the template permits of an outward displacement of the feeler 29, the pressure in conduit 34- drops, the valve piston 32 rises, the discharge conduit 25 is opened wider by the throttling edge 37, and the pressure in conduit 23 and the force of the holder-up are reduced. When forging is terminated, the gripping head 3 is pushed back to the right, the pump 38 supplies oil to,

The forging operation is performed as follows:

The workpiece 21 or 22 is first gripped in the gripping head 3. Pressure is applied to the piston 16 by fluid supplied through the conduit 29 to feed the mandrel 13 or 14 to a position between the hammers 1. Then the feed movement of the gripping head 3 is initiated, whereby the holder-up 10 is forced backwardly and the workpiece is moved between the hammers. When the cartridge chamber is to be forged (FIGS. 4 to 6), an enlarged portion of the mandrel 14, which corresponds to the cartridge chamber, abuttingly engages a bottom surface 41 of a cup shaped insert 42 in the gripping head sleeve 7 in the last phase of the feed movement workpiece. To make this possible, the cylinder 17 is displaced in the cylinder 13 by pressure applied through the conduit 19 against the hydraulic force from conduit 20. This movement of the cylinder 17 and of the piston 16 causes that portion of the mandrel 14 which is to be used for shaping the cartridge chamber to enter the space between the hammers. in order to ensure that axial flow of workpiece material will take place only in the direction toward the gripping head under the combined action of the gripping forces acting in the longitudinal direction and of the radially acting forging forces during the forging of the internal step between the barrel and the cartridge chamber, a groove 43 in the insert 42 defines a protruding annular portion 44, over which the displaced material can slide (FIG. 6). For the same purpose, the rear end of the workpiece may be provided with an annular recess 45, which is upset during the forging of a step as shown in dotted lines (FIG. 7). If the workpiece has a uniform outside diameter, the hydraulic back-pressure of the holder-up 16 is not increased until the cartridge chamber is shaped during the final phase of the forging operation in order to ensure the shaping of a satisfactory internal step.

What is claimed is:

1. In a machine of the type described, in combination:

(a) a support;

(b) hammer means movable on said support toward and away from a forging area;

(0) a mandrel positioned on said support in said forging area and adapted to be received in a hollow workpiece while the same is being forged, said'workpiece having two end portions;

(a') gripping means for moving said workpiece through said area in a predetermined direction, said gripping means including (1) gripping head means movable on said support in said direction and having an end face adapted abuttingly to engage one end portion of said workpiece, said end face being formed with a protruding annular portion having an outside diameter which is smaller than that of the workplece, p

(2) holder-up means movable on said support in said direction and adapted to engage the other end portion of said workpiece,

(3) first pressure-fluid operated means for actuating said movement of said gripping head means, whereby a gripped workpiece and said holder-up means are moved in said direction when movement of said gripping head means is actuated by said first pressure fluid operated means; and

(4) second pressure-fluid operated means connected to said holder-up means for opposing movement of the same by the actuated gripper means; and

(0) pressure fluid control means for varying the pressure of the fluid operating said second pressure-fluid open ated means responsive to the position of said gripping head means during movement of said gripping head means on said support.

2. In a machine of the type described, in combination:-

(a) a support;

(b) hammer means movable on said support toward and away from a forging area;

() a mandrel positioned on said support in said forging area and adapted to be received in a hollow workpiece while the same is being forged, said workpiece having two end portions;

(d) gripping means for moving said workpiece through said area in a predetermined direction, said gripping means including (1) gripping head means movable on said support in said direction and adapted to engage one end portion of said workpiece,

(2) holder-up means movable on said support in said direction and adapted to engage the other end portion of said workpiece,

(3) first pressure-fluid operated means for actuating said movement of said gripping head means, whereby a gripped workpiece and said holder-up means are moved in said direction when movement of said gripping head means is actuated by said first pressure fluid operated means; and

(4) second pressure-fluid operated means connected to said holder-up means for opposing movement of the same by the actuated gripper means;

(e) pressure fluid control means for varying the pressure of the fluid operating said second pressure-fluid operated means responsive to the position of said gripping head means during movement of said gripping head means on said support; and

(f) means mounted on said support and constituting a hydraulic resistance, a hydraulic cylinder independently displaceable on said support against said hydraulic resistance, a piston slidable in said cylinder, and a rod freely extending through said gripping head means and connecting said mandrel to said piston, said gripping head means having an engaging surface arranged to engage said mandrel and to displace the same and said cylinder during said movement of said gripping head means in said direction.

3. In a machine as set forth in claim 2, said mandrel being stepped.

4. In a machine of the type described, in combination:

(a) a support;

([9) hammer means movable on said support toward and away from a forging area;

(0) a mandrel positioned on said support in said forging area and adapted to be received in a hollow workpiece while the same is being forged, said workpiece having two end portions;

(d) gripping means formoving said workpiece through said area in a predetermined direction, said gripping means including (1) gripping head means movable on said support in said direction. and adapted to engage one end portion 'of said workpiece,

(2) holder-up means movable on said support in said direction and adapted to engage the other end portion of said workpiece,

cluding (1) a cylinder member and a piston member movable insaid cylinder member, 7

(2) one of said members of the second pressure fluid operated means being mounted on said support, the other member being connected to said holder up means for movement thereby; and

(e) pressure fluid control means for varying the pres sure of the fluid operating said second pressure-fluid operated means responsive to the position of said gripping head means during movement of said gripping head means on said support, said control means including (1) valve means connected to said cylinder memher for controlling'displacernent of liquid from said cylinder member during movement therein of said piston member,

(2) scanning means having a template member and a feeler member, one of the members of said scanning means being mounted on said support, and the other member being connected to said head means for joint movement therewith, said scanning means being connected to said valve means for controlling the displacement of said liquid responsive to the position of said 40 head means scanned by saidscanningmeans.

References Gated by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 5/59 Germany. 1/02 Great Britain.

RICHARD H. EANES, JR, Primary Examiner.

warn/roan A. WILTZ, Examiner. 

1. IN A MACHINE OF THE TYPE DESCRIBED, IN COMBINATION: (A) A SUPPORT; (B) HAMMER MEANS MOVABLE ON SAID SUPPORT TOWARD AND AWAY FROM A FORGING AREA; (C) A MANDREL POSITIONED ON SAID SUPPORT IN SAID FORGING AREA AND ADAPTED TO BE RECEIVED IN A HOLLOW WORKPIECE WHILE THE SAME IS BEING FORGED, SAID WORKPIECE HAVING TO END PORTIONS; (D) GRIPPING MEANS FOR MOVING SAID WORKPIECE THROUGH SAID AREA IN A PREDETERMINED DIRECTION, SAID GRIPPING MEANS INCLUDING (1) GRIPPING HEAD MEANS MOVABLE ON SAID SUPPORT IN SAID DIRECTION AND HAVING AN END FACE ADAPTED ABUTTINGLY TO ENGAGE ONE END FACE ADAPTED WORKPIECE, SAID END FACE BEING FORMED WITH A PROTRUDING ANNULAR PORTION HAVING AN OUTSIDE DIAMETER WHICH IS SMALLER THAN THAT OF THE WORKPIECE, (2) HOLDER-UP MEANS MOVABLE ON SAID SUPPORT IN SAID DIRECTION AND ADAPTED TO ENGAGE THE OTHER END PORTION OF SAID WORKPIECE, (3) FIRST PRESSURE-FLUID OPERATED MEANS FOR ACTUATING SAID MOVEMENT OF SAID GRIPPING HEAD MEANS, WHEREBY A GRIPPED WORKPIECE AND SAID HOLDER-UP MEANS ARE MOVED IN SAID DIRECTION WHEN MOVEMENT OF SAID GRIPPING HEAD MEANS IS ACTUATED BY SAID FIRST PRESSURE FLUID OPERATED MEANS; AND (4) SECOND PRESSURE-FLUID OPERATED MEANS CONNECTED TO SAID HOLDER-UP MEANS FOR OPPOSING MOVEMENT OF THE SAME BY THE ACTUATED GRIPPER MEANS; AND (E) PRESSURE FLUID CONTROL MEANS FOR VARYING THE PRESSURE OF FLUID OPERATING SAID SECOND PRESSURE- FLUID OPERATED MEANS RESPONSIVE TO THE POSITION OF SAID GRIPPING HEAD MEANS DURING MOVEMENT OF SAID GRIPPING HEAD MEANS ON SAID SUPPORT. 